Bituminous compositions in hydraulic constructions

ABSTRACT

A method is provided for the stabilization of a water permeable breakwater construction composed of open layers of stone or block. This method includes the steps of applying a viscous bituminous composition in discrete patches on the lining surface of the stone or block layers to form a discontinuous layer of the bituminous composition on the lining surface and then flowing the bituminous patches downwardly through the lining surface to thereby extend the discontinuous layer of the bituminous composition beneath the lining surface. The finished breakwater construction has openings which extend completely through the bituminous layer and all the layers of stone or block.

limited States Patent Span et a1.

[451 Jan. 13, 1972 [541 BITUMINOUS COMPOSITIONS IN HYDRAULIC CONSTRUCTIONS [72] lnventors: l-lylco J. Th. Span, De Bilt; Albert J.

Woestenenk, l-lintham, both of Netherlands [73] Assignee: Bltumarin N.V., Zaltbommel, Netherlands [22] Filed: Dec. 2, 1969 [21] Appl. No.: 881,607

[30] Foreign Application Priority Data Dec. 16, 1968 Great Britain v.59,690/68 [52] U.S.Cl .f. ..61/4,61/37 [51] Int. Cl. ..E02b 3/06 [58] Field oiSearch ..61/3, 4, 35, 36, 37, 38, 30

[56] References Cited UNITED STATES PATENTS 1,973,821 9/1934 Mason ..61/30 2,130,044 9/1938 Subkow et a1. ..61/30 1,352,429 9/1920 Clarke ..61/37 1,987,152 1/1935 Mason ..61/4

Primary Examiner-David J. Williamowsky Assistant Examiner-David H. Corbin Attorney-Jones & Lockwood ABSTRACT A method is provided for the stabilization of a water permeable breakwater construction composed of open layers of stone or block. This method includes the steps of applying a viscous bituminous composition in discrete patches on the lining surface of the stone or block layers to form a discontinuous layer of the bituminous composition on the lining surface and then flowing the bituminous patches downwardly through the lining surface to thereby extend the discontinuous layer of the bituminous composition beneath the lining surface. The finished breakwater construction has openings which extend completely through the bituminous layer and all the layers of stone or block.

8 Claims, 3 Drawing Figures Pmmwmwmz 3.635.033

INVENTORS HYLCO J. TH. SPAN ALBERT J. WOESTENEM 7m wmf/m ww AT TORN EYS BITUMINOUS COMPOSITIONS EN HYDRAULIC CONSTRUCTIONS Hydraulic works, such as dikes, dams, jetties and break waters are usually subject to severe attacks either by waves or by currents. Measures are, therefore, taken to protect such works as far as possible against the action of the wash of waves and currents, e.g., by lining the slopes thereof with basalt or concrete blocks or with heavy stones. However, it has been observed that such a lining cannot, ultimately, withstand the action of water unless artificial elements of very large dimensions were chosen. in particular, at high tide and in stormy weather, linings of normally available stones are not stable enough to withstand the heavy wave attack and currents. A stabilization against such attack can be obtained by grouting with bitumen or bituminous compositions, so that a water-impermeable construction is obtained.

it has been observed that such a construction has certain drawbacks due to its impermeability to water giving rise to the building up of water pressure which may impair the stability of the revetment.

The building up of water pressure under the revetment of a bank may be caused by tide movements, down drag, and steady seepage of water due to a high-ground-water level.

The invention relates to the use of bituminous compositions for the stabilization against wave attack of banks, dikes and dams in such a way that the building up of water pressure under the armor or revetment (hereinafter referred to as linings) is substantially prevented. Accordingly, the invention relates to a method for stabilization against wave attack of hydraulic works like banks, dikes and dams having linings made of stones or blocks which method comprises laying a bituminous composition, as hereinafter defined, in patches which penetrate into the lining and thereafter form a discontinuous layer undemeath the surface of the lining.

By bituminous composition is understood a mixture of bitumen and mineral aggregate (including filler) having a bitumen content larger than corresponds with the voids volume of the mineral aggregate. The bitumen may be any bitumen generally employed for road building. Tar and pitch and mixtures of tar and bitumen may also be used.

Generally, any bituminous composition within the definition given above may be used for the method of grouting according to the invention. Grouting is carried out by pouring the bituminous composition on the open stone layer(s) forming the lining. The bituminous composition penetrates the whole depth of the open stone layer(s) and subsequently flows away sidewise. The depth of penetration is normally controlled by a sublayer having much smaller pores than the stone structure to be grouted. When laying penetrating patches care is taken that underneath the surface of the stone layer(s) (the stone structure) no water-impermeable layer is formed resulting from a too extended sidewise flow of the penetrating bituminous composition. Such careful penetrating lies, of course, within the capability of the expert. According to a particular aspect of the invention a bituminous composition is used which simplifies the laying of the penetrating patches in that the depth of penetration and the sidewise flow of the composition through the stone structure is controlled. According to this aspect of the invention a bituminous composition is used that is built up in such a way that it can be considered as a mixture of a bituminous mortar and stones, wherein the size of the stones is chosen in relation to the size of the stones in the stone structure to be grouted such that the upper size D 85 of the stones in the bituminous composition is 5 to l0 times smaller than the lower size D of the stones to be penetrated.

Bituminous mortar is any mixture of bitumen with aggregate consisting of filler and either sand, broken stone, or gravel or with any combination of sand, broken stone or gravel, the mixture of bitumen and aggregate having a bitumen content larger than corresponds with the voids volume of the aggregate. Mortars usually have a bitumen content of 10 percent w. or more, preferably at least 12 percent w.

Lower size D 15 means the sieve width expressed in equivalent diameters through which 15 percent of the stones pass; upper size D means the sieve width expressed in equivalent diameters through which 85 percent of the stones pass.

Of course, the bituminous composition is heated before grouting to a temperature at which the composition can be poured, to penetrate the stone structure. The viscosity of the bitumen present in the bituminous composition may be adapted to the flow requirements set to the composition.

The bituminous mortar content of the preferred bituminous compositions is preferably at least 35 percent w. A very suitable composition is one having a mortar content of at least 45 percent w, the rest of the composition consisting of stones and the bitumen content of the mortar being 12 percent w.

In a lining consisting of more than two layers of stone, the depth of the penetration is preferably such that the upper two layers of stones are penetrated.

A lining of three layers of stone of which the upper two layers are grouted according to the invention is very suitable as a defense against wave attack.

The patches are preferably arranged on the lining in such a way that the discrete patches are as close to each other as possible. The patches may touch each other and they are preferably laid in a regular pattern.

Preferably, at least 50 percent of the total voids volume of the lining to be penetrated is filled with the bituminous composition, in particular 50-75 percent of the voids volume is filled.

Preferably, the patches each have similar areas, i.e. as similar as is possible when laying the patches under the prevailing working conditions. The weights of the patches are, in principle, chosen in response to the working methods and available equipment. A good rule of thumb for the determination of the required minimum weight of a patch is the complete filling of the voids volume of two layers of stone over a surface of 0.8-1.0 dF, the two layers together having a thickness of d. meters. The maximum weight for a patch may be chosen two to three times the required minimum weight. Once the weight of a patch being chosen, the spacing of the patches depends on the desired degree of grouting of the total lining, which corresponds with the filling of, preferably, at least 50 percent of the voids volume of the total lining as said before.

When the patches are laid, the bituminous composition penetrates between the stones of the lining and, as explained above, the upper size D 85 of the stones in the preferred bituminous composition is five to 10 times smaller than the lower size D 15 of the stones to be penetrated. Stones of linings having stone-weights of 1,000 to 6,000 kg. have a lower size D 15 of 75 cm., so that the stone size in the bituminous composition in this example may have an upper size D 85 of 7.5 to 15 cm. Suitable bituminous compositions contain 55 percent stones with equivalent diameters of 10-20 cm. (upper size D 85 of 15) and 45 percent bituminous mortar comprising crushed stone of a size up to 12 mm., the bitumen content of the mortar being 12 percent w. Such bituminous compositions having a temperature of about C. may penetrate between the stones of the stone structure to a depth of two stones, that is up to 2 meters for stones having a weight of 1,000 to 6,000 kg.

Referring to the drawing, FIGS. 11, 2 and 3 illustrate a preferred embodiment of the patch-grouting system of this invention.

FIG. 1 is a cross-sectional view, in elevation, of a breakwater composed of open stone layers in which patches of bituminous material are disposed upon open stone layers according to this invention;

FIG. 2 is an enlarged fragmentary view of a portion of the layers of open stone and bituminous patches depicted in FIG. 1; and

FIG. 3, is an enlarged fragmentary top plan view of the surface of the breakwater construction depicted in FIGS. 1 and 2.

FIGS. 1 and 2 are cross-sectional views of a pattem-grouted lining for a breakwater construction consisting of bituminous patches 1, open large stone layers '2, smaller stone layers 3 and a core layer of quarry run 4.

FIG. 3 is a surface view of the lining of the breakwater construction showing the bituminous patches 1 laid in a regular pattern which penetrates a portion of the open stone layers 2.

As can be most clearly seen from FIG. 2, the bituminous composition of the patches 1 penetrates the depth of the open stone layers 2 and flows sideways beneath the upper stones of the lining surface to form a discontinuous bituminous layer underneath the surface of the lining. As shown by the stones protruding between the arrested bituminous patch flow in FIG. 2, no water impermeable layer is formed at the lining surface or underneath the lining surface as a result of a too extended sidewise flow of the penetrating bituminous composition of the patches. Further, from FIG. 3 it is seen that the bituminous patches 1 may be arranged in a regular pattern so as to touch each other without fomiing a water impermeable layer on the surface of the open stone layer 2.

The patches themselves, penetrated between such stones, have a weight of at least 6,400 kg. according to the rule of thumb given above, assuming that the lining to be grouted has a voids volume of 40 percent and a specific gravity of 2.5 for the patches. For example, sufficient stabilization is obtained when using patches having a weight of 12,000 kg., the patches being laid in rows with distances of 5 meters between the patches and the spacing between the rows being 2.5 meters, the total of the patches filling 50 percent of the voids in the lining. When using patches having a weight of 8,000 kg., the total of the patches filling 65 mrcent of the voids in the lining, the patches are laid in rows with distances of 3.5 meters between the patches and with a spacing between the rows of 1.75 meters.

The technical advantages of the above method of pattern grouting can be illustrated as follows: The stability of discrete elements forming a revetment against wave attack can be characterized by the so-called stability factor k,, of the wellknown Hudson formula. When applying the grouting method of the invention, the k value of the stone can be multiplied by a factor of which the value on the basis of the present experience with the method of the invention is at least 5. This means that a revetment after pattern grouting has gained a stability as if the revetment would consist of discrete elements five times as heavy.

A continuous and complete grouting as carried out in the art would have given disappointing results owing to the building up of water pressures underneath the resulting water-impermeable revetment.

We claim:

1. A method for making a water permeable breakwater construction composed of open layers of stone or block having openings extending through said layers. the outennost layer of which forms a lining surface for the breakwater construction, which method includes the steps of:

a. adjusting the temperature and consequently the viscosity of a bituminous composition to a flow condition such that the composition can penetrate at least the lining surface of said open layers,

. applying the viscous bituminous composition in discrete patches on the lining surface to form a discontinuous layer of the bituminous composition on the lining surface, and

c. flowing said bituminous patches downwardly through the lining surface and sideways beneath the lining surface to extend the discontinuous layer of the bituminous composition through and underneath the lining surface, said discontinuous bituminous layer leaving openings underneath the lining surface for the passage of water therethrough so that the finished breakwater construction has opening which extend completely through the discontinuous bituminous layer and all the layers of stone or block. 2. The method of claim I in which the discrete patches of step (b) are applied in a regular pattern on the surface of the lining.

3. The method of claim 1 in which the bituminous composition is a mixture of bituminous mortar and stones, said stones having an upper size D 85 from five to 10 times smaller than the lower size D I5 of the stones of the open layers of the linmg.

4. The method of claim 3 in which the bitumen content of the bituminous mortar is at least 10 percent by weight.

5. The method of claim 3 in which the bituminous composition has a mortar content of at least 35 percent by weight.

6. The method of claim 3 in which the bituminous composition consists of 45 weight percent of mortar and 55 weight percent of stones, the bitumen content of the mortar being 12 percent by weight.

7. The method of claim 1 in which the open layers consist of more than two layers and the viscosity of the bituminous composition is adjusted such that the bituminous composition penetrates the open layers to a depth of at least two layers.

8. The method of claim 1 in which 50 to percent of the voids volume in the open stone layers is filled with the bituminous composition of the discrete patches.

1: w: a a e 

2. The method of claim 1 in which the discrete patches of step (b) are applied in a regular pattern on the surface of the lining.
 3. The method of claim 1 in which the bituminous composition is a mixture of bituminous mortar and stones, said stones having an upper size D 85 from five to 10 times smaller than the lower size D 15 of the stones of the open layers of the lining.
 4. The method of claim 3 in which the bitumen content of the bituminous mortar is at least 10 percent by weight.
 5. The method of claim 3 in which the bituminous composition has a mortar content of at least 35 percent by weight.
 6. The method of claim 3 in which the bituminous composition consists of 45 weight percent of mortar and 55 weight percent of stones, the bitumen content of the mortar being 12 percent by weight.
 7. The method of claim 1 in which the open layers consist of more than two layers and the viscosity of the bituminous composition is adjusted such that the bituminous composition penetrates the open layers to a depth of at least two layers.
 8. The method of claim 1 in which 50 to 75 percent of the voids volume in the open stone layers is filled with the bituminous composition of the discrete patches. 